Gas phase stabiliser-free production of hydrogen peroxide using supported gold-palladium catalysts

Hydrogen peroxide synthesis from hydrogen and oxygen in the gas phase is postulated to be a key reaction step in the gas phase epoxidation of propene using gold–titanium silicate catalysts. During this process H2O2 is consumed in a secondary step to oxidise an organic molecule so is typically not observed as a reaction product. We demonstrate that using AuPd nanoparticles, which are known to have high H2O2 synthesis rates in the liquid phase, it is possible to not only oxidise organic molecules in the gas phase but to detect H2O2 for the first time as a reaction product in both a fixed bed reactor and a pulsed Temporal Analysis of Products (TAP) reactor without stabilisers present in the gas feed. This observation opens up possibility of synthesising H2O2 directly using a gas phase reaction

Silica Bifunctional Supports for the Direct Synthesis of H2O2: Optimization of Br/Acid Sites and Pd/Br Ratio

[EN] We have studied the direct synthesis of hydrogen peroxide using a catalytic system consisting of palladium supported on silica bifunctionalized with sulfonic acid groups and bromide in the absence of acid and halide promoters in solution. Catalysts with several bromide substituents were employed in the catalyst synthesis. The prepared samples were characterized by TXRF, XPS, and hydrogen peroxide decomposition. Catalysts characterization indicated the presence of only palladium (II) species in all of the samples, with similar values for surface and bulk of Pd/Br atomic ratio. The catalysts were tested via direct synthesis, and all samples were able to produce hydrogen peroxide at 313 K and 5.0 MPa. The hydrogen peroxide yield and selectivity changed with the Pd/Br ratio. A decrease in the Pd/Br ratio increases the final hydrogen peroxide concentration, and the selectivity for HO reaches a maximum at a Pd/Br ratio around 0.16 and then decreases. However, the maximum hydrogen peroxide concentration and selectivity occur at slightly different Pd/Br ratios, i.e., resp. 0.4 vs. 0.16.This research was funded by SOLVAY (Brussels)

Silica Bifunctional Supports for the Direct Synthesis of H₂O₂: Optimization of Br/Acid Sites and Pd/Br Ratio

We have studied the direct synthesis of hydrogen peroxide using a catalytic system consisting of palladium supported on silica bifunctionalized with sulfonic acid groups and bromide in the absence of acid and halide promoters in solution. Catalysts with several bromide substituents were employed in the catalyst synthesis. The prepared samples were characterized by TXRF, XPS, and hydrogen peroxide decomposition. Catalysts characterization indicated the presence of only palladium (II) species in all of the samples, with similar values for surface and bulk of Pd/Br atomic ratio. The catalysts were tested via direct synthesis, and all samples were able to produce hydrogen peroxide at 313 K and 5.0 MPa. The hydrogen peroxide yield and selectivity changed with the Pd/Br ratio. A decrease in the Pd/Br ratio increases the final hydrogen peroxide concentration, and the selectivity for H2O2 reaches a maximum at a Pd/Br ratio around 0.16 and then decreases. However, the maximum hydrogen peroxide concentration and selectivity occur at slightly different Pd/Br ratios, i.e., resp. 0.4 vs. 0.16

Carbon-supported palladium catalysts for the direct synthesis of hydrogen peroxide from hydrogen and oxygen

Twelve kinds of carbon materials were studied as supports of palladium catalysts for the direct synthesis of hydrogen peroxide. The correlation between the catalytic performance and the structure and physicochemical properties of carbon materials suggested the important roles of the graphitic structure and the surface function groups in the selective formation of H2O2. The carbon material with a higher degree of graphitic structure and a lower density of surface COOH groups provided higher H2O2selectivity and productivity. The chemical state and the mean size of Pd particles also affected the catalytic behavior. Metallic Pd was more efficient than PdO, and the catalyst with a smaller mean size of Pd nanoparticles exhibited higher activity and H2O2selectivity. The presence of a mineral acid rather than a halide promoter and an organic solvent contributed to the selective formation of H2O2. ? 2014 Elsevier Inc. All rights reserved